Green Infrastructure: Trees and Their Vital Role in City Sustainability

By Emily Ball

Green infrastructure has become a buzzword in urban planning and sustainability — it refers to the framework and benefits cities can harness by building, preserving, or maintaining a resilient natural system. And what is one of the most vital and practical components of green infrastructure? Trees.

Benefits of robust canopy coverage

Trees play a crucial role in many cities’ sustainability goals. Increasing tree canopy cover over time significantly impacts a community’s sustainability efforts — from reducing the heat island effect and intercepting storm water, to storing and sequestering carbon, supporting wildlife habitats, and enhancing livability. However, while green infrastructure is increasingly recognized as an essential aspect of sustainability, the great impact of trees is often overlooked.

Understanding the current canopy coverage and making achievable goals for future coverage is crucial for the planning and management of green infrastructure. Cities can use online resources, like the i-Tree Canopy tool by the U.S. Forest Service or the Growing Shade tool hosted by the Metropolitan Council, to understand current canopy coverage and areas to improve.

Understanding tree species diversity is also an essential part of taking inventory and future planning of a resilient community forest. Cities that have a more diverse inventory of tree species limit the risk of being greatly impacted by invasive species and pests like emerald ash borer.

Best practices for increasing and maintaining coverage

From rapidly developing to fully developed communities, it is important to sync up community forestry and green infrastructure goals with city ordinances, planning processes, and comprehensive planning. Many believe that new housing developments can lower the number of trees in a community, but that isn’t always the case. In some instances, new housing developments are created on land that was previously used for farming that had little-to-no canopy coverage.

If a city has a strong developer agreement in place that requires planting after construction, with specifications and standards ensuring trees are properly planted, a greater canopy could be fostered. A community might not discover a trend like that until they perform an i-Tree Canopy analysis and look back over time to find patterns.

A best practice when building housing in wooded areas is to determine which trees are in the best health and condition, then keep their roots protected to the edges of the canopy during construction. A look at the tree species and sizes will also inform whether they can survive the process. Additionally, trees do better in a cohort of other trees, so developments may try to keep groups of trees near each other and choose to cut down a sole tree on the property where its root zone is likely to be compacted with equipment.

Construction project planning also considers where to place equipment and how to enter and exit the construction site, all focusing on protecting the trees on the developed land. Unless a planning code has performance standards, staff or consultants, and a method to carry out this work with developers, the community’s green infrastructure and canopy will be negatively impacted.

Connecting trees and sustainability planning

Challenges in communities around increasing canopy coverage and quantifying tree species diversity include budget constraints, lack of staff, or conflicting priorities from city leaders or the public. However, cities should measure the success of their sustainability planning on metrics related to species diversity and canopy coverage. This can be achieved by obtaining an accurate inventory of existing trees and current canopy cover, and creating short-, mid-, and long-term goals and benchmarks for each.

Asset management software has made it easier to edit tree inventory data, with workers in the field able to take a picture or add attributes from their phones. More research on the benefits and ecosystem services of trees has also significantly improved the ability to quantify the benefits of proactive forestry management.

Additional canopy cover factors to consider

One of the biggest challenges facing cities today is the emerald ash borer, a pest causing significant canopy loss and public health risks due to dead, brittle ash trees in the landscape. Cities need to realize this and act immediately to inventory, budget, and educate. Residents need to be educated on the importance of tree coverage and the risks to ash trees. Many do not realize that a tree can take as long as a human lifetime to mature fully, and that an ash tree may be saved and preserved for the community’s benefit with periodic injections.

In addition to being a crucial part of green infrastructure, trees can significantly impact social equity. Areas where a majority of the residents are considered low income or identify as Black, Indigenous, or people of color are often affected by limited tree canopy coverage, leading to heat islands and other environmental challenges. Grants to improve tree management and canopy cover are available on an ongoing basis through the Minnesota Department of Natural Resources, which encourages community forestry projects to focus on increasing canopy coverage in areas of environmental justice concern.

A robust forestry management plan has a positive impact on a community’s sustainability efforts. Increasing tree diversity and canopy cover over time improves livability and environmental health. Let’s not overlook the critical role trees play in creating green infrastructure and achieving sustainability goals.

Emily Ball is forestry program manager with WSB (wsbeng.com). Contact: eball@wsbeng.com. WSB is a member of the League’s Business Leadership Council (lmc.org/sponsors).